1. Field of the Invention
This invention relates to a magnetic head feed device, and more particularly to a magnetic head feed device comprising a rotational motion-linear motion converting means for converting a rotational motion of a rotating motor into a linear motion of a magnetic head.
2. Description of the Prior Art
In a magnetic recording/reproducing system using a magnetic recording disk, e.g., an electronic camera, there is generally required a magnetic head feed device for feeding the magnetic head in a radial direction of the magnetic recording disk placed on a spindle.
The magnetic head feed device is generally driven by a rotating motor such as a stepping motor or a DC motor, and accordingly, there is required a rotational motion-linear motion converting means for converting a rotational motion of the motor into a linear motion of the magnetic head.
There has been known a rotational motion-linear motion converting means in the form a feed screw unit comprising a spur gear driven by a rotating motor, a shaft portion which has the spur gear integrally and coaxially therewith and is provided on a part of the outer surface with a male thread portion, and a pipe portion having a female thread portion in mesh with the male thread portion of the shaft portion so that the shaft portion is linearly moved when it is axially rotated.
Since the female thread portion of the pipe portion is generally formed from one end of the pipe portion as a matter of manufacturing convenience, an end portion of the female thread portion is exposed as the shaft portion is linearly moved and there is a possibility that dust is deposited on the exposed portion of the female thread portion. When dust is deposited on the female thread portion, accuracy in feeding the shaft portion is lowered and load on the motor is increased.
Since the other end portion of the pipe portion functions as a guide for guiding the linear motion of the shaft portion, a relief portion must be formed between the guide portion and the female thread portion. The work of forming the relief portion is very difficult especially when the diameter of the female thread portion must be small.